1. Field of the Invention
This invention relates to a pneumatic apparatus for classifying particles of refuse material and the like, to separate relatively light and heavy particles. In particular, this invention relates to a column classifier through which air is drawn from bottom to top and which has an air locked feed chute that opens into the column intermediate the top and bottom, for admitting mixed light and heavy particles to the rising air stream, with the heavier particles dropping from the column while lighter particles are carried upwardly in the air stream.
2. Description of the Prior Art
Pneumatic devices for classifying and separating solid particles in an apparatus that includes a column with a stream of air rising therethrough, are known to the prior art. To facilitate describing the distinguishing features of the present invention from the prior devices, such prior devices can be categorized as comprising two types. A first type includes a column in which mixed solids are dropped into the top of the column in which a stream of air is rising; and a second type includes a column in which mixed solids are fed at an intermediate elevation into the column in which air is rising.
Examples of apparatus of the first type appear in U.S. Pat. Nos. 1,365,884 of Aug. 21, 1923, 1,650,727 of Nov. 29, 1927; 1,787,759 of Jan. 6, 1931; and 3,833,117 of Sept. 3, 1974.
Examples of the second type appear in U.S. Pat. Nos. 2,968,400 of Jan. 17, 1961; 3,265,210 of Aug. 9, 1966; and 3,441,131 of Apr. 29, 1969.
As will appear from the description to follow, the present invention relates to the aforesaid second type and has for its object the location and utilization of a baffle which is pivotal to control air flow characteristics to provide an improved control effect upon separation characteristics in that type of classifier-separator. In such regard, it should be noted that among the prior patents referred to and related to both types, are disclosures of pivotal baffle-like devices at locations and for purposes other than as shall be hereinafter described and claimed. For example, in U.S. Pat. No. 1,465,884, a pivotal damper is provided to control an air inlet opening into one side of the lower end of a solids separating column; in U.S. Pat. No. 1,787,759 a pair of relativel pivotal plates are used to control air inflow to a particle separator; and in U.S. Pat. No. 2,968,400 a pivotal plate adjustably directs a generally horizontal flow of air and light particles through a drop-out chamber after heavy particles have dropped out in a vertical chamber. In addition, applicants are aware that devices of the aforesaid second type have been built with a pivotal plate controlling the flow of air drawn upwardly of a mid-column level at which solids are injected into the air stream.
None of the aforesaid practices of the prior art have involved a pivotal baffle located to operate in the manner that will be described with regard to the present invention.